Ortho-phenylphenol (OPP) is useful in aqueous systems due to its biocidal activity. OPP has proven especially effective in controlling pathogenic organisms and viruses. As such, OPP is often useful as an active ingredient in disinfectant formulations for homes and hospitals. OPP is often added to metalworking fluids, cosmetics, toiletries and ceramics to control spoilage or decomposition. OPP may also be applied to leather goods to impart mold resistance.
In order to keep shipping costs down, OPP is often sold and shipped in 100 percent active form, i.e., solid form. Unfortunately, handling of solid OPP has disadvantages. One disadvantage is that dust may occur which can be flammable. Another disadvantage is that the solid form is not easily added to an aqueous system via automation due to the difficulty of metering solids. Yet another disadvantage is that the OPP may not be easily dispersible in the aqueous system and vigorous agitation may be required.
For the above reasons, in some applications it may be desirable to employ OPP in a liquid formulation. Usually, OPP is dissolved in a liquid such as an organic solvent or a mixture of organic solvent and water.
Unfortunately, a disadvantage of liquid formulations comprising OPP and organic solvents is that said formulations are fairly expensive due to the cost of the organic solvents. In addition, the formulations have a reduced active concentration and reduced physical stability, i.e., inhomogeneity may result upon freezing and thawing. Yet another disadvantage of liquid OPP formulations which employ organic solvents are the environmental concerns associated with the organic solvents.
One such environmental concern is that increased chemical oxygen demand of the industrial waste water, e.g., cooling tower effluent, results when OPP is employed with organic solvents. Chemical oxygen demand represents the amount of oxygen consumed in the oxidation of organic and oxidizable inorganic material contained in the waste water. See Richard J. Lewis, Hawley's Condensed Chemical Dictionary, Twelfth Edition, 1993, p. 253. A high chemical oxygen demand is undesirable for a body of water whether the body be a wastewater treatment pool or a natural body of water.
A high chemical oxygen demand for a body of water is undesirable because biodegradation of microorganisms may cause oxygen depletion in said body of water. If the body of water is a wastewater treatment pool then oxygen depletion could be detrimental to the efficient operation of the wastewater treatment plant. If the body of water is a natural body of water then oxygen depletion could be detrimental to aquatic life which require oxygen for survival.
Formulations comprised of OPP and organic solvents contribute more chemical oxygen demand than if OPP is employed alone or with non-organic solvents because organic solvents serve as a feeding ground for microorganisms by providing nutrients. Therefore, even though the OPP may destroy a majority of the microorganisms before it degrades, a few microorganisms still survive. Those few microoganisms multiply very rapidly in the presence of an organic solvent. Therefore, when OPP-treated waste water containing an organic solvent is released to the environment, or even if it is in a closed system, chemical oxygen demand will increase significantly over time due to the rapidly multiplying microorganisms consuming oxygen in the water.
It would be desirable to discover liquid formulations of OPP that utilize water as a suspending medium. This type of formulation would not only reduce the chemical oxygen demand as compared to formulations which employ organic solvents, but such a formulation would also be less expensive with water replacing the organic solvent. It would also be advantageous if a wide range of OPP concentrations could be usefully employed in the formulations. Furthermore, it would be desirable if the formulations were insensitive to changes in temperature.